HELP!!! This car is driving us crazy!

[sable227]

We have a 1993 300zx non-TT and AT. We noticed that the car was hesitating when accelerating so we changed the spark plugs, injectors, fuel rail seals, TPS, cleaned the MAF. We also put new mufflers on because the old ones had large holes in them and needed to be replaced. Now we have a larger problem. When we were driving the car, we noticed black smoke coming from the exhaust and the mufflers started to get a red glow. Before we changed the mufflers, we did not have the black smoke. The other thing we noticed was that the car would shift ok from 1st to 2nd, but would not shift from 2nd to 3rd and the rpms were running really high. Could someone please help us figure out what the problem might be?

[audtatious]

Cleaning the MAF can cause issues which could make the vehicle run rich. As far as the mufflers getting a red glow do you mean they are getting hot? If so then you may have fuel burning off in the mufflers which is really odd as the catalytic converters may have issues at this point as well. Check your MAF, validate you have the right size injectors as well. Pull a spark plug to see what they look like now.

[sable227]

Hi and thank you for responding. The muffler getting hot happened back in February and the car has been sitting in the driveway since then. The muffler was so hot, it melted the wiring insulation underneath the trunk carpet. The injectors are for the car. We put the spark plugs in last week and cleaned the MAF three days ago with the proper cleaner. Two days ago, we fired the car up and filled it with gas. We still have the black smoke and the issue with the car not shifting from 2nd to 3rd. The old mufflers were in very bad shape and had to be replaced (huge hole in the driver's side). But even before then, we noticed some hesitation in the car when accelerating. We love the car and we want to get it running. Any ideas or suggestions are welcome. Thanks in advance.

[DCaff300ZX]

The only things that come to mind here for me are that if the mufflers were very shot, perhaps the catalytic converters are as well and perhaps one of the new injectors is leaking into the cylinder and exhaust...black smoke would be the case but with some severe drivability issues as well I'd think. It may sound odd, but have you tested to be sure exhaust can flow out that hot muffler (hand near muffler tip while running) and it's not somehow plugged?
Also, I assume that you had a shop do the injectors and other repairs, if so have you contacted them about this?

[sable227]

Thank you for replying. The black smoke started before we switched out the injectors. We are leaning towards the opinion that the catalytic converters might be toast.